He can tame a horse - a white horse? (7)
I believe the answer is:
breaker
'he' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'tame a horse a white horse?' is the wordplay.
I cannot really see how this works, but
'tame' could be 'break' (breaking is a kind of taming) and 'break' is located in the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
'can' is the link.
Can you help me to learn more?
(Other definitions for breaker that I've seen before include "User of CB radio" , "Heavy wave arriving on the shore" , "Wave with white crest" , "Wave hitting the shore" , "Large sea wave" .)